code: def sig(x):
      return 1.0 / (1.0 + np.exp(-x))
  
imports: from builtins import zip
  import numpy
  import pprint
  import pytest
  from neon import NervanaObject
  from neon.backends.autodiff import Autodiff
  from utils import allclose_with_out
label_desc: Use image node_id 1 for calling the CustomFunc obj's underlying member method code with example usage: obj.sig(x) and returns: unknown